This installation method would not disturb what's there in a serious way, as the new gypsum would be pressed up against what's there.My understanding is that it's a common and accepted practice to cover up some forms of asbestos, for instance, layering new tape on top of the old white asbestos duct-work insulation I believe is a common approach. 

That would include new duct work, and a 2 1/2 ton unit.

So lets just take some wild guesses here:Professional Mold remediation guesstimate 10KFully gut and replacement of kitchen (depending on size and quality level of upgrades) can average 10K - 35K.Bathroom full gut and replace 5K - 15K (depending on fit and finish)Central Heat and Air for a 2 Ton unit 10K depending on type, and if you need duct work add another 3K-8KInterior paint 2KExterior paint 2K-5KUsing reverse cost estimating for contingencies add another 7.5K - 10K So just guestimating your looking at 95K rehab costs.

Courtney is talking about a ductless mini-split heat pump, which could be installed in an occupied unit with limited disruption.Installing a traditional ducted system would be more invasive due to the necessity of installing the duct work.

Has a hot water baseboard heat (gas) and no ductwork.

I had my gas furnace & AC unit replaced in November, by my HVAC guy who's done 6 figures worth of business with me over the years and gives me preferential pricing, and it still cost me almost $6k for a higher-end unit and that was with no ductwork requirements.

If the hvac is a forced air system, perhaps it may help to clean the duct work.

Personally I have decided to suspend any repairs unless urgent.I have one tenant that needs new ductwork scheduled this Thursday.  

A large opossum managed to get into our ductwork, and died between the walls that were used as a plenum for the heating system! 

Can I mount this 4” pipe basically at the grate of the air return and run it through this air return (just drywall) until it hits the basement ductwork?